# How Long Will A 12 Volt Battery Run A Fan? (A Short Guide)

Wondering how long a 12v battery will power a fan during summer camping? You're in the right place.

This is going to be a short but on-the-point guide to figuring out the 12v battery runtime on any size fan.

To determine how long will a 12v battery run a fan will depend on a few factors:

1. Battery Capacity (Ah)
2. Battery DoD limit
3. Fan wattage consumption
4. Inverter efficiency

How Long Will A 12 Volt Battery Run A Fan? in short, a 12v 70Ah lead-acid battery (with a 50% DoD limit) will run a portable 12v 50W DC fan for about 8.4 hours.

Need a simple solution? Use Our battery runtime calculator to find out.

## Calculate how long a 12v battery will power fan

Battery Capacity
Ah
Battery Volts
V
Select Battery Type
Wh

Now let's dive deep into some calculation stuff so again you'd never have to use any calculator to figure out the backup time of your battery.

## 12v Battery Capacity in watts

There are mainly 3 types of batteries, lead-acid, AGM, and lithium.

Lead-acid, and AGM batteries have a DoD (depth of discharge) limit of 50%. Which means you can only discharge them half. But the lithium (LiFePO4) batteries can be fully discharged up to 100%.

This was just a basic overview of batteries if you're a noob. Now let's get into some calculation stuff.

First, let's calculate the battery capacity in watts from amp-hours (because the fan's capacity is measured in watts).

Battery capacity in Watt-hours = Battery Ah * Battery Volts

### For Example

Let's suppose you have a 12v 100Ah lead-acid battery.

``100*12 = 1200Wh or 1.2kWh``

To calculate the useable Wh multiply the value by 2 for lead-acid, AGM, and gel battery types (Because of their 50% depth of discharge limit).

``1200 * 0.5 = 600Wh``

You have 600 Wh of useable power stored in a 12v 100Ah lead-acid battery.

This guy has explained wonderfully about batteries. watch this if you're a beginner.

Related Post: Amps To Watts Calculator: How Many Watts In A 12-volt Battery?

## Inverter Efficiency

An inverter will be required to run an AC fan (which consumes 120-220V input). But some small fans required DC current (12v) which you can run directly from a 12v battery.

When converting DC into AC there will be some power loss because usually, inverters are only 85-90% efficient.

This means a 100W inverter will consume 100W DC power from the battery bank and only will be able to output 85-90 AC watts.

So if you're running an AC or DC fan with an inverter with a 12v battery then minimize the DC to AC conversion loss from battery watt-hour capacity.

### For example:

Let's continue with the previous example. 12v 100Ah lead-acid battery.

``600 * 0.85 (for 85% inverter efficiency) = 510 AC watts``

You would get 510 AC watts from a 12v 100Ah lead-acid battery with a 50% depth of discharge limit.

Related Post: Solar DC Watts To AC Watts Calculator

## How Long Will A 12 Volt Car or Deep Cycle Battery Run A Fan? Chart

Here's a chart showing how long a 12v 50Ah lead-acid battery will run a fan.

Note: Check the input wattage consumption of your fan in the product description session (usually located on the back side of every fan) and make the calculations for you accordingly.

## What size inverter do I need to run a fan?

There is one rule of thumb. Multiply the wattage consumption of your fan by 1.2 when selecting the size of an inverter.

For example, to run a 50W fan you would need a 60-watt inverter.

But yes obviously you're not just gonna run a fan with an inverter. So keep in mind the above rule of thumb to select the size of an inverter according to your need.

Related Post: How Long Will a 12v Battery Last With 500w Inverter?

## Summary

To calculate how long a car or 12v battery will run a fan, Divide the battery amp-hours by the fan input amps. but it will completely discharge the battery which you can achieve only with a lithium battery, if you have a lead-acid, AGM, or Gel battery type then the runtime will be half.